Hartquist, TW, Wagner, AY, Falle, SAEG et al. (2 more authors) (2011) Cosmic Rays and Radiative Instabilities. In: Marcowith, A, Bykov, A, Ferrière, K and Montmerle, T, (eds.) Memorie della Societa Astronomica Italiana. Cosmic Rays and their InterStellar Medium environment: CRISM 2011, 26 Jun - 01 Jul 2011, Montpellier, France. Fabrizio Serra editore , pp. 836-841.
Abstract
In the absence of magnetic fields and cosmic rays, radiative cooling laws with a range of dependences on temperature affect the stability of interstellar gas. For about four and a half decades, astrophysicists have recognised the importance of the thermal instablity for the formation of clouds in the interstellar medium. Even in the past several years, many papers have concerned the role of the thermal instability in the production of molecular clouds. About three and a half decades ago, astrophysicists investigating radiative shocks noticed that for many cooling laws such shocks are unstable. Attempts to address the effects of cosmic rays on the stablity of radiative media that are initially uniform or that have just passed through shocks have been made. The simplest approach to such studies involves the assumption that the cosmic rays behave as a fluid. Work based on such an approach is described. Cosmic rays have no effect on the stability of initially uniform, static media with respect to isobaric perturbations, though they do affect the stability of such media with respect to isentropic perturbations. The effect of cosmic rays on the stability of radiative shocked media depends greatly on the efficiency of the conversion of energy in accelerated cosmic rays into thermal energy in the thermalized fluid. If that efficiency is low, radiative cooling makes weak shocks propagating into upstream media with low cosmic-ray pressures more likely to be cosmic-ray dominated than adiabatic shocks of comparable strength. The cosmic-ray dominated shocks do not display radiative overstability. Highly efficient conversion of cosmic-ray energy into thermal energy leads shocked media to behave as they do when cosmic rays are absent.
Metadata
Item Type: | Proceedings Paper |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © SAIt 2011. This is an author produced version of a conference paper published in MEMORIE della Società Astronomica Italiana. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | shock waves; ISM: kinematics and dynamics – ISM: cosmic rays; hydrodynamics; instabilities; ISM: clouds |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 28 Feb 2020 16:01 |
Last Modified: | 28 Feb 2020 16:01 |
Published Version: | http://sait.oat.ts.astro.it/MSAIt820411/index.html |
Status: | Published |
Publisher: | Fabrizio Serra editore |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:130889 |